They aren't a storage company, they are a company who facilitates transactions and like any other bitcoin business needs to securely store their btc.
The original comment was about them being similar to a bank which just isn't true at this point, it isn't what their business is about.
I don't get how you see a bank? As a storage company or money that just sits there doing nothing? Or as a company that facilitates transactions not unlike Coinbase?
They're very much like a bank in that regard. And yes they do also put a big focus on storage, it's not their only thing but they have one of the most popular wallets (2 million), claim to hold the most amount of bitcoin for users, more than any other company in the world, have a multi-sig product, have a vault product, have an insurance on their wallets, have mobile wallets, an SMS wallet, a web wallet.
This idea they're not about storing bitcoin (as well as other things) is ridiculous.
Are they a bank? In some ways, sure. Is that bad? No. A bank just offers financial services, and that's awesome.
And if you offer those financial services in a currency that can't be forged by criminals or printed and debased to fund an illegitimate military adventure, on a network that can't be blocked, is open to all, transparent and requires no permission, and offer products like a multi-sig wallet that put 100% of control with the user and 0% control with Coinbase as a choice to the user, that's awesome.
That may be a bank in that they offer financial services, but it's a lot better to me.
That's quite simply wrong; they are the most popular online wallet there is. You simply cannot make this claim, it's patently untrue.
So how do they make money from it? By stealing your assets, like most Bitcoin wallet companies?
Wrong. There's a reason they call one of their services a "wallet" - because they hold other people's bitcoins. And guess what, they now have a USD wallet too, for storing other people's USD (http://avc.com/2015/01/feature-friday-us-dollar-wallet/)
And as gnaritas said, they are not an exchange, they have a broker service.
The original post was about them being like a bank, which is not true in the context of their business model.
Yet. Like the OP said, "Next up they'll probably offer interest and loans/mortgages". Who knows what else they'll divert their attentions to (hint: it's probably where the money is).
Coinbase seems to be going for the Payment Processor route, now with the USD wallet who knows if they'll offer you a CC just like Xapo. Guess who else offers you CCs?
but usd wallets are definitely something novel (bitstamp also allows you to hold usd, but not for the use cases that coinbase is enabling)